Hydraulic control system for moving clamping members on a lift truck laterally, independently of each other, and simultaneously in the same and opposite directions



May 18, 1965 K. H. BERGE 3,134,083

' HYDRAULIC CONTROL SYSTEM FOR MOVING CLAMPING MEMBERS ON A LIFT TRUCK LATERALLY, INDEPENDENTLY OF EACH OTHER, AND SIMULTANEOUSLY IN THE SAME AND OPPOSITE DIRECTIONS Filed Sept. 11, 1961 4 Sheets-Sheet 1 4o 32 30 H6. 24 IO r1. 1 v so 20 22 56 60 I4 FKB. 8 FIG. 9

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r VIP use g 19s INVENTOR 22o KENNETH H. SERGE.

BY 94 228 98 88 w ATTORNEY May 18, 1965 K. H. BERGE 3,184,033

HYDRAULIC CONTROL SYSTEM FOR MOVING CLAMPING MEMBERS ON A LIFT TRUCK LATERALLY, INDEPENDENTLY OF EACH OTHER, AND SIMULTANEOUSLY IN THE SAME AND OPPOSITE DIRECTIONS Filed Sept. 11. 1961 4 Sheets-Sheet 2 FIG. 2 62 72 64 iROM PUMP TO SUMP I02 FIG. 5

INVENTOR KENNETH H. BERGE 2 [O4 ATTORNEY M y 1965 K. H. BERGE 3,184,088

HYDRAULIC CONTROL SYSTEM FOR MOVING CLAMPING MEMBERS ON A LIFT TRUCK LATERALLY, INDEPENDENTLY OF EACH OTHER, AND SIMULTANEOUSLY IN THE SAME AND OPPOSITE DIRECTIONS Filed Sept. 11. 1961 4 Sheets-Sheet 3 INVEN TOR.

KENNETH H. SERGE 102 ATTORNEY y 8, 1965 K. H. BERGE 3,184,088

HYDRAULIC CONTROL SYSTEM FOR MOVING CLAMPING MEMBERS on A LIFT TRUCK LATERALLY, INDEPENDEN'ILY OF EACH OTHER, AND SIMULTANEOUSLY IN THE- SAME AND OPPOSITE DIRECTIONS Filed Sept. 11. 1961 62 4 Sheets-Sheet 4 FIG. 6 1 h 50 64 INVENTOR v KENNETH H. BERGE ATTORNEY United States Patent l HYDRAULEQ CONTRGL SYSTER I FOR MGVING CLAMPENG MEMBERS 9N A LIFT TRUCK LAT- ERALLY, ENDEPENDENTLY 6F EAGH UTHER, AND SEMULTANEGUSLY EN TEE SAME AND @PPGSH'E DERECTIONS Kenneth H. Berge, Battle (Jreelr, Mich, assignor to @larl;

Equipment Company, a corporation of Michigan Filed Sept. 11, 1961, Ser. No. 137,157 Claims. (Cl. 21 F653) This invention relates to material handling apparatus, and more particularly to improvements in load clamping mechanism for use with industrial lift trucks of the type having its load elevating carriage equipped with a pair of load engaging members.

When operating lift trucks of the above type, it is frequently necessary to maneuver the truck so as to bring load engaging members thereof, such as load grip or clamping arms, into registry with or in symmetrical disposition relative to a predetermined load pick-up or depositing location, such as when removing loads from a stack of material, or stacking material, or conforming to a general predetermined load location pattern. Not infrequently the first attempt at attaining such registry or symmetrical disposition is not successful, necessitating one or more additional attempts on the part of the operator requiring extra maneuvering operations which, of course, add to the cost of handling the material. In stacking containerized material in confined spaces, such as box-cars and the like, it is frequently necessary to rearrange the material during loading operations so as to make room for additional containers in order to maximize the use of available loading space. Furthermore, less skillful operators of lift truck equipment frequently have diiriculty in centering loads to be engaged between the clamp arms preparatory to clamping the load.

The present invention constitutes an improvement or" the device of US. Patent No. 2,795,346, issued June 11, 1957, in the provision of an improved control system for such devices which makes possible controlled movements of load engaging clamp arms in all possible combinations. In using my invention it is possible to control the clamp arms so as to shift the same laterally of the truck in either direction in unison without increasing or decreasing the distance between the arms, to actuate the arms simultaneously in opposite directions for opening and closing the clamp arms relative to one another, and to actuate either one of the clamp arms in either direction independently of any movement of the other clamp arm.

It is therefore a primary object f the present invention to provide in a lift truck of the type having a pair of load engaging arms mounted for lateral movement on the truck and means connected to the arms to shift the arms laterally of the trucn While maintaining the spacing therebetween, a means operatively connected to the arms for operating either one of the arms laterally of the truck while the other arm remains stationary.

It is a further object of the present invention to provide in a lift truck of the type having a pair of load engaging arms mounted for lateral movement on the truck, control means for simultaneously shifting the arms toward or away from one another to enable the arms to clamp or to release a load therebetween, to shift the arms laterally of the truck in either direction while maintaining the same spacing therebetween, and to shift either one or the other of said arms laterally of the truck in either direction independently of the other arm.

A further object of the present invention is to provide in a lift truck of the type having a pair of load engaging arms mounted for lateral movement on the truck, control means for shifting both arms toward or away from gdddfi h Patented May id, 1985 one another to enable the arms to clamp or to release a load therebetween, and to operate either of the arms toward or away from the other arm while the other arm remains stationary.

In the drawings:

FIGURE 1 is a perspective view of an industrial lift truck which embodies the present invention, said lift truck being of the type having load grip arms which are shown in somewhat extended condition;

FIGURE 2 is a schematic view of the hydraulic system for controlling movement of the load grip arms, the system being shown in its neutral condition;

FIGURE 3 is a view similar to FIGURE 2 but showing the system in condition for holding one arm stationary while causing the other arm to move away from the first arm;

FIGURE 4 is a view similar to FIGURE 3, but showing the moving arm being actuated toward the stationary arm;

FIGURE 5 is a view similar to FIGURE 2, but showing the system in condition for releasing a load with both arms moving away from one another;

FIGURE 6 is a view similar to FIGURE 2, but showing the system in condition for shifting a load to the left, as viewed in the drawing;

FIGURE 7 is a view similar to FIGURE 6, but showing the system in condition for shifting a load to the right; and

FlGURES 8, 9 and 10 are longitudinal sectional views showing one of the manually controlled valve units in three diiierent positions for variously controlling the movement and location of one of the clamp arms.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, numeral 1%) indicates generally an industrial lift truck which embodies the present invention. This vehicle includes a body portion 12 which is mounted on four wheels in the usual manner. On the truck illustrated, the wheels 14 are drive wheels and operated by prime mover means located Within body portion 12. The rear wheels 16 are dirigible wheels and are connected to an operators steering wheel 26 by means of a conventional linkage for steering the vehicle. The operators station, of which the steering wheel 20 is a part, includes also seat 22 and various controls for operating the vehicle, the lifting mast, and the attachment device which is the subject of the present invention.

At the front end of the body portion of the truck is located the vertically disposed telescopic mast structure 24. This mast is pivotally mounted at its lower end on the body portion of the truck and is arranged to be tilted forwardly and rearwardly by conventional means, including a link and bracket 26 and 28 connected between truck mounted hydraulic cylinder means (not shown) and the mast structure 24 at each side thereof. The mast structure 24 includes an outer guide rail formed by a pair of channel members 30 and an inner slide structure formed by a pair of I-beam section members 32 which telescope within corresponding members of outer guide structure 30, 343. A load supporting carriage 34 is arranged to be moved upwardly and downwardly on the inner slide structure 32, 32 by means of a plurality of brackets and rollers, not shown, which support the carriage in the inner slide structure in known manner. Elevation of the carriage in mast 24 is produced in a conventional manner by a hydraulic motor 38 comprising an outer cylinder and an inner piston (not shown) which is arranged to raise and lower the carriage through a chain and sprocket mechanism 40 (only the chains are shown). The chains 4% are reeved over sprockets supported from the upper end of the piston rod, being secured to carriage 34 at the one ends thereof and to the truck body at the level.

' from suitable pump means, not shown.

. 3 opposite ends thereof. levation of thepiston rod of hydraulic motor 38 elevates carriage 34 in the inner slide structure 32, 32 by means of chains, and said inner slide structure in the outer guide members 3%, 359 in known manner.

Mounted on carriage 34 is an asscmbly including a pair of load clamp arms 56} and 51 each having a generally C-sha-ped base portion 52 secured at its ends to a pair of tubular slides 54 which are slidably received within tubular guides 56. The guides of one arm are interspersed with respect to the guides of the other arm, as shown, the arms being arranged on their bases to compensate for this arrangement of the guides in a manner such that the arms are disposed at the same horizontal Tubular guides s extend through and are fixed to carriage 34. These tubular guides are slotted at 58 to accommodate the ends of C-shaped base portions 52 to thus allow for a considerable amount of travel of the arms and to enable the arms'to be brought into fairly close proximity to one another. Each pair of adjacent ends of tubular guides 56 is connected by a cross piece 66.

Associated with each arm 59 and 51 is a hydraulic actuator, the upper actuator in FIGURE 1 being indicated by numeral 62 and a lower actuator being indicated by numeral 64. Each actuator includes a cylinder 66 connected at 63 to the cross piece 6t) remote from the associated arm. Each cylinder contains a piston 76 (FIG. 2) having a piston rod 72 extending from the cylinder and connected to the base portion 52 of the associated arm. a

The clamp arm structure so far described is shown in the above-identified patent. The present invention includes in combination withclamp arm structure such as exemplified by the foregoing description, a novel bydraulic control system for controlling the movement of the clamp arms, and will now be described with reference to FIGS. 210. V

The hydraulic system which is shown in neutral condition in FIG. 2, includes a plurality it interrelated spring loaded check and pilot vaive units 86, 82, 84 and 8d hydraulically intermediate hydraulic actuators 62 and 64 and a plurality of operator control valve units 88, 0 and 92. The control valve units'are connected by inlet conduits 94, 96 and 93 to a common conduit 1% which conducts hydraulic fluid to said control valves The control valves also connected to a sump or reservoir, not shown, by means of a common conduit 102 and conduits 104, 1G6 and 168. The control valves are preferably mounted on the lift truck at the operators station in a location not shown, but convenient for manual control during operation of the truck. As shown for the sake of convenience, control valves 88, 9t and 92 are independently housed, but may, if desired, be readily combined valve units may also be readily combined in a single.

valve housing as will be apparent to persons skilled'in 'the art. The various check valve units may be of identical construction, although this is nota requirement. As

. illustrated, the various check valve units are of the same designand the following description thereof relates equally asjwell to each of the four valve units.

Each of the check' valve units comprises a housing 116 having a passageway therethrough which consists of chambers 118 and 129 formed opposite ends of the housing and a relatively small diameter passage 122 connecting said chambers. A ball check valve 124- is located in each chamber 129 and is urged into seated and sealing relation with the one end of each passage 122 by a spring 126. A floating piston-like pilot valve 128 is located in each chamber 118 and has projecting from the upper side thereof a stem 13% which is adapted to move the respective ball check valve 124 upwardly against the pressure of spring 123' so as to permit communication between passage 122 and chamber 12%. Opening of any one of the ball check valves will occur when chamber 118 beneath the associated pilot valve is subjected to hydraulic pressure which actuates the pilot valve toward the ball check valve to unseat the latter.

Cylinder actuators 62 and 64 define piston rod chambers 132 and 13 i, and cylinder chambers 136 and 133, respectively. Control valve unit 9% is adapted to be connected to cylinder chamber 136 by way of conduits 140, 142 and 144, and to cylinder chamber 138 by way of conduits 14 5, 148 and 15h. Conduits 140 and 146 are also connected to chambers 12% of check valve units 56 and 82, respectively. The piston rod chambers 132 and 134 are connected to chambers 12% of valve units 89 and 84 by means of conduits 152 and 154, respectively, said latter conduits and piston rod chambers being connected to each other by a cross-over conduit 15s. It will be noted that this circuitry operates in conjunction with control valve unit. 90 and by-passes the ball check valve 124 of each check valve unit 853, S2, 84 and 86. Upon actuation of control valve 63 out of a neutral position this circuitry effects equal side shifting movement in the same direction of clamp arms 5% and 51 in a manner which will be described in detail in conjunction with FIGS. 6 and 7.

Control valve unit 88 may be actuated in one direction to be connected simultaneously to pilot chamber 118 of check valve 80' and to passage 122 of check valve 32 by a conduit 150 and an interconnecting conduit .162, as shown; Contrariwise, control valve 88 may be actuated in the opposite direction to be simultaneously connected to passage 122 of valve unit t and to the pilot chamber 118 of valve unit $2 by way of a common conduit 11 and conduits 164 and 166. This circuitry which connects control valve 88 to check valves and 82, together with conduits 1458,15 3, 1552, 154 and 156, controls movements to the left and to the right of the clamp arm 51 which is associated with actuator 64, while clamp arm 59 remains stationary, as will be decribed in detail hereinbelow in conjunction with FIGS. 3 and 4. V i

Control valve 92 is adapted to be connected simultaneously to pilot chamber 118 of check valve unit 34 and to connecting passage 122 of check valve unit 36 by means of a conduit 17d and an interconnecting conduit 172. Contrariwise, control valve 92 is adapted to be connected to the pilot chamber of check valve unit and to the connecting passage of check valve unit 84 by means of a commonconduit 1'74 and connecting conduits 17 .5 and 178. This circuitry which connects. control valve unit 92 to check valve units 8% and $6, together with conduits142, 144, 152, 154, and 156 controls movements tothe left and to the right of the clamp arm which is associated with actuator 62, while the other clamp arm 5% remains stationary, as will be Preferably, the various conduits described above which connect control valve units 88 and 92 to the check valve units and to the cylinder actuators, and the conduits which connect check valve unit 94; to the cylinder actuators, are flexible to simplify ease of assembly. The check valve units may be, and have been in actual commercial practice, connected to mounting plates, not shown, located on the rear side of carriage 34 and tubular guides 56 so that the check valve units move in elevation with the carriage along the elevating mast structure of the truck. With the control valve units 88, 9t) and 92 mounted on the body of the truck for convenient operation by the driver, it is then necessary to provide relatively long and flexible conduits 149, 146, res, 151, 170 and 174 which are of sufficient length to follow the vertical movements of the check valve units on the carriage. Various means for mounting the control and check valve units relative to each other and to the carriage 34 are known, and further discussion with respect thereto is not deemed necessary.

Referring now to FIGURES 8, 9 and 10, the details of a control valve unit is illustrated which is suitable for use at each control valve unit station 88, 9t and 92. Since these control valve units are substantial duplicates of each other, only control valve 88 is shown in three different conditions of operation. In the neutral position of valve 88 (P16. 8) control lever 11% is in an upright position, it being connected to one end of a movable spool valve 18% which is mounted in a longitudinal bore 182 which extends through valve housing 184. A plurality of spaced port control spool elements 186, 188, 1% and 192 on valve member 1% are slidable in bore 182, and stem sections 194, 196 and 198 connect said spool elements. A va-lve support spool element Zlit) is supported in bore 182 at the one end of the housing and is connected to spool element 192 by stem section 262. A passageway 294 extends longitudinally and centrally of the stem of spool valve 18% from the plugged right end thereof to spool element 188. Passage 2 34 communicates with openings 266, 298 and 216 which extend diametrically through stern portions 262 and 196. A passage 212 receives hydraulic fluid from the pump through conduit 94; a passage 214 connects passage 212 to the sump by way of conduits 164 and 102 when the spool valve is in a neutral position, and continuously connects a housing chamber 216 to sump conduit rat by way of a passageway 218. An annular port 226 in the housing 184 is connected to conduit 160, and an annular port 222 in the housing is connected to conduit 161. A passage 224 is adapted to communicate pressure fluid from the pump to a valve chamber 225 through a spring loaded ball check valve 228 upon actuation of the spool valve ldti to either the position shown in PEG. 9 or PEG. 10.

With the spool valve in neutral position, discharge from the pump communicates directly with the sump by way of conduits ms, 94 and 212, the annular opening provided in the control valve housing by stem section 194, and conduits 214, 164 and 102. The pump does not, under this condition, generate pressure sufiicient to open check valve 223, and ports 228 and 222 are blocked from communication with chamber 226 by spools 190 and 192, respectively. Therefore, with control valve lever lit) in a neutral position, hydraulic fluid cannot how to or from clamp arm actuator 64 by way of control valve 88. Similarly, with valve levers 112 and 114 in neutral fluid cannot flow to or from actuators 62 or 64 by way of control valves 9% or 92.

Actuation of control valve lever 110 forwardly, as shown in FIG. 3, actuates spool valve 18% outwardly of bore 182, as shown in FIG. 9, which causes spool element 188 to close passageway 214 and communicates annular port 22% and conduit 16% with chamber 226, whereby pressure fluid flows from the pump through the check valve 228 into chamber 226, and thence around valve stem section 19% into port 220 and conduit 16%. At the same time conduit 161 is vented to the sump by way of annular port 222, around stem section 2% into chamber 216, and conduits 218, 214, i434 and 182. Actuation of valve lever to the position shown in PEG. 4 actuates spool valve to a clamp position, as shown in FIG. 10, wherein spool section 186 now interrupts communication between pump passageway 212 and sump passageway 214, and pressure fluid is conducted from the pump through the check valve 228 to conduit 161 by way of chamber 226 and port 222, the sump connection now being by way of conduit res, port 22%, valve opening 21%, passageway and openings 204, 268 and 206, chamber 27.6, and passageways 218 and 214 to sump conduits, 1M and 102.

As pointed out above, control valve units 88, 9d and 92 may be essentialy identical to each other and are each adapted to control in the manner described above the flow of fluid to and from the pair of conduits connected to each control valve unit which corresponds to conduits T and 161 of valve unit 88. In the combination hydraulic control circuit of the present invention it has been found desirable to provide in the spools 192 of each of control valve units 83 and 92 a U-shaped groove 23a? formed in the periphery of spool 192 for the purpose of bleeding off residual pressure fluid in port 222 and the conduit connected thereto for a purpose to be described hereinafter.

Operation It will be appreciated that under the condition illustrated in FIG. 2 wherein each of the control valves 38, 9t) and 92 are located in neutral position, ball check valves 124 of check valve units 8%, 82, 84 and 86 are in closed position, and that each of the conduits connected to the control valve units are blocked from communication with the pump conduit 1% or the sump conduit 102 so that the clamp arms 5'9 are maintained in the position illustrated. Throughout the following description of operation open will refer to relative opening movement of clamp arms 50, and closed will refer to relative closing movement of said clamp arms. Directions of clamp arm movement will be referred to in the same sense as indicated by the arrows in each of the figures illustrating different conditions of operation. In FIGS. 2-7 arrowed lines have been applied only to those conduits and passageways in which fluid is flowing for the illustrated condition of operation.

In FIG. 3 control valve units 90 and Q2 are located in neutral position and lever 11% of unit 88 is actuated to open clamp arm 51 while clamp arm 50 remains stationary. Since fluid flow is blocked through valves 93 and 92, fluid can only flow through valve 83, which is positioned in the condition illustrated in FIG. 9. Pressure fluid from the pump therefore flows through port 22! of valve 83 to conduit ltitl which enters pilot chamber 118 of check valve 86 to actuate pilot piston 128 upwardly to unseat ball check 1124, thereby communica'e ing actuator chamber 134 with the sump conduit E32 by way of conduits 15d and 152, valve chamber and passage 126 and 122, conduit 161, valve port 222 and conduits 218, 214 and me. Simultaneously, pressure fluid is conducted to connecting passageway 12.2 of check valve unit 82 which unseats the ball of unit 82, whereby pressure fluid flows to cylinder chamber 138 by way of conduits 148 and 15%. It will be noted that conduit 146, which is connected to conduit 148, is pressurized, but no fluid flows therethrough since conduit 146 is connected to control valve unit 90 which is in a neutral position. Likewise conduit 152 is connected to actuator chamber 132 and to discharge flow conduit 156, but no movement of clamp arm 56 can occur inasmuch as cylinder chamber 136 is also connected to closed control valve 536 by way of conduits 144, 142 and Mil. Thus, clamp arm 50 remains stationary as clamp arm 51 moves in an opening direction relative thereto, check valve units 8i) and $2 being open and check valve units 84 and 3:) remaining closed.

Referring now to FIGUREA valve lever 11% is actuated to an opposite or clamp closing position wherein the pressure connections of conduits 169 and 161 in valve unit 88 are reversed as shown in FIG. 10, and pump pressure fluid flows through valve unit 88 and conduit 161 to the pilot chamber 118 of check valve 82 and to the connecting passage 122 of check valve 80, thus actuating the pilot in valve unit 82 to unseat the ball check and pressurizing'the ball check of valve unit 811 directly to unseat same. Pressure fluid then flows through valve unit 81) to the piston rod chamber 134 by way of conduits 152 and 156 which actuates clamp arm 51 in a closing direction toward clamp arm 50, hydraulic fluid being forced from cylinder chamber 138 to the sump by way of conduits 159 and 143, open check valve 82, conduits 162 and 169, valve unit 88, and conduits 1G4 and 192. As'explained above with respect to opening operation of clamp arm 51, clamp arm 5% remains in fixed position even though piston rod chamber 132 thereof is connected to pressure fluid conduit 152 since cylinder chamber 136 of the latter actuator cannot exhaust fluid by Way of conduits 144, 142 and 1417 through control valve 96, which is in neutral position. The latter conduits, as well as the cylinder chambers of actuator 62, are pressurized, but no fluid can flow therethrough and clamp arm 51 remains in fixe position. It will also be noted that the ball checks of valve units 84 and 86 are subjected to pressure fluid in a valve closing direction, and no fluid can flow through these check valves. 7

From the foregoing operation of FIGS. 3 and 4 it will be apparent that independent movement of clamp arm 5% is controlled by valve units 92, 84 and $6 in the same manner as such movement of clamp arm 51 is controlled by valve units 88, $1) and S2. Briefly, actuatiton of valve lever 114 to the position of lever 116m FIG. 3 causes clamp arm 51? to move open to the right relative to arm 51 which remains stationary, pump discharge pressure being conducted to conduits 179 and 172 which opens both check valve units 84 and 86. Pressure fluid flows through check valve 86 and conduits 142 and 144 to cylinder chamber 136 of actuator 62 which actuates clamp arm 51 in an opening direction and ejects fluid from piston rod chamber 132 through conduits -2, 156 and 15 1-, check valve unit 84-, conduits 176 and-174, port 222 of control valve unit 92 and conduits 19S and 162 to the sump. Contrariwise, movement of control lever 114 to the position of control lever 11%) in FIG. 4 actuates clamp arm 55 toward clamp arm 51 in a closing direction by reversing the connections of control ports 22% and 222 in controlvalve 92, causing pump pressure fluid to flow through check valve 84 and conduits 154, 156 and 152 to piston rod chamber 132 of actuator 62, fluid being ejected from;

cylinder chamber 136 through conduits 144 and 142, open check valve 86, conduits 172 and 17d, contol valve 92,

and conduits 1&8 and 1132 to the sump. During such independent movement of clamp arm 51?, control valve units 88 and 91? remain in a neutral position, check valve units 3G and 82 remain closed, and conduit connections of arm actuator 64 terminate in a closed passage in control valve unit it? and at a closed check valve unit.

Referring now to FEGURE 5,1 have illustrated a mannor of operatingcontrol valve units 88 and 92'to-gether, while'valve 90 remains in neutral position, so that clamp arms 51? and 51 can be actuated simultaneously in opposite directions for either clamp closing or opening movement. As illustrated, the valve units 88 and 5 12 have been actuated to move the clamp arms in'opening simultaneously together in closing movement as will be apparent from the description which follows.

' *Inthe condition of operation illustrated, check valve units 86 and'SZ are subjected to pressure forces the same g passing pressure fluid to cylinder chamber 138. Check valve units 84 and 86 are also open with valve unit 86 receiving pressure fluid from conduit 172 and passing same through conduits 142 and 144 to cylinder chamber 136. In this mode of operation, fluid which is ejected from piston rod chambers 132 and 1%- follows the path of least resistance, chamber 132. ejecting fluid through check valve 89 and control valve 88, and chamber 134 ejecting fluid through check valve 1 and control valve 92 to the sump. Fluid in cross-over conduit 156 tends to remain static, as does fluidin conduits 140 and 146-bittween closed control valve 91! and conduits 142 and 148. Clamparms 50 and 51 are therefore actuated simultaneously in opening movement. Similarly, actuation of control valve levers 119 and 114 to an opposite position causes the clamp arms to move simultaneously in a closing direction. Again, all four check valve units are open. In this instance pressure fluid follows the path of least resistancabeing conducted to chamber 132 of actuator 62 by control valve 88, check valve 81 and conduit 152, and to chamber 134 of actuator 64 by control valve 92,

check valve 34 and conduit 15 4. Again fluid in crossover conduit 156 tends to remain static, as does fluid in conduits 14th and 146 as mentioned above. Fluid is ejected from actuator chamber 136 through check valve 86 and control valve 92, and from actuator chamber 138 through check valve 82 and control valve 88.

In FIGURE 6 the clamp arms 5'19 and 51 are shown in engagement with a load and shifting that load leftwardly, and in FIGURE 7 said clamp arms are shifting a load to the right. It will be understood that the load in each of these instances has been previously engaged in accordance with one of the available modes of operation described above in conjunction with FlGURES 3, 4 and 5, and is now being shi ted to the left or to the right for the purpose, for example, of depositing the load in an elf-center position relative to the truck, or for shifting ,the load to a centered'position relative to the truck following pick-up thereof in an off-center location. It will also be readily appreciated that the clamp arms can be.

first side shifted to the right or to the left preparatory to clamping a load which is off-center relative to the center-line of the truck, and to approximately locate the clamp arms as required, subsequent to which the arms may be independently or simultaneously actuated, as desired, to clamp the load therebetween. In FIGURE 6 control valve levers 1113 and 114 are in neutral positions and valve lever 112 is actuated forwardly. Pressure fluid is conducted by conduits 1951 and 96 to port 220 of valve so and thence to cylinder actuator chamber 138 by way of conduits 11-6, 143 and 151i. Clamp arm 51 will therefore be actuated leftwardly by actuator unit 64, which action discharges fluid from piston rod chamber 134 to piston rod chamber 132 of actuator unit 62 by way of conduits 154,156 and 152. closed circuit between actuator chambers 132 and 134 since check valve units hi? and 84 remain closed during this operation as will be apparent. Piston 70 of actuator unit 62, along with clamparm 50, is therefore actuated leftwardly with clamp arm 51 and discharges fluid from cylinder chamber 136 to the sump by way of conduits 144,

142, 140, 166 and 1il2 through port 222 of control valve 99. Since actuator units62and'64are of the same design, the volume of fluid transferred from chamber134 to chamber 132 during such movement of clamp arm 51 causes equal movement of clamp arm in the same direction and at the same rate as arm 51, so that the load is shifted leftwardly with the clamp arms while being engaged thereby with the same clamping'force as was initially applied thereto by the clamp arms. In other words,

"the load will neither tend to be dropped nor crushed as described 'above in respect of FIGURES, and both of 7 these check valves are therefore open with check valve 82 during such shifting movement. It will be noted that all of the check valve units 80, 82, $4 and 86rernain closed during side shifting movement of the clamp arms.

Shifting movement of the'clamp arms to the right is V This fluid is trapped in the.

open.

t accomplished by actuating control valve lever 112 to an opposite position, as shown in FIGURE 7, wherein the uid flow pattern of the control system is the reverse of that described above in respect tof FIGURE 6, as illustrated by the arrowed lines in FIGURE 7.

Referring again to FIGURE 8, groove 230 is provided in spool element 192 of each of control valves 88 and 92, but not in control valve $0, for the purpose of relieving residual pressure fluid in conduits ldl, 164, 174 and 176 following either indepedent or simultaneous load clamping movement of clamp arms 5% and 51. Referring to FIGURE 4, for example, wherein clamp arm 51 is shown in closing operation, it will be appreciated that without groove 230 or an equivalent means for connecting valve port 222 to chamber 216, return of valve lever 119 to neutral position would tend to trap pressure fluid in conduits 161 and 164, which residual pressure would slowly bleed off to the sump through control valve 88. In the interim such residual pressure would hold check valve 82 If side shift control valve 90 were actuated prior to bleed off of such residual pressure, it will be seen from FIGURE 6 that pump pressure would be communicated through open check valve 82 to pilot chamber 118 of check valve 80, thus tending to open the latter valve. Pressure fluid transfer between piston rod chambets 134 and 132 would therefore be vented to the residual pressure lines 161 and 164 which would tend to cause a relaxation of the gripping force of clamp arm 50 on the load and a possible dropping of the load. Groove 23% connects port 222 to sump pressure chamber 216 so that conduits 161 and 164 are bled-ofi-immediately to sump pressure upon return of valve lever 110 to a neutral position, thereby permitting check valve unit 82 to immediately close. Likewise, a groove 230 is pro vidcd in control valve unit 92 to effect rapid closing of check valve unit 86 following clamping movement of clamp arm 50 and return of valve lever 114 to a neutral position. The various control valve units 88, 9t) and 92 can therefore be operated in any sequence as above-described and without delay between the return of one of the valve levers to neutral and the actuation of another of said control valve levers.

The present invention provides a novel and relatively simple hydraulic circuit controlling operation of clamp arms for the purposes specified above whereby the two clamp arms or load engaging members which are mounted for movement toward and away from one another may be conditioned for movement either to the left or to the right in exact unison so that a load being carried thereby is shifted therewith in one or the other directions with continued maintenance of initial clamping pressure on the load, or either one of the load engaging members may be shifted leftwardly or rightwardly independently of the other load engaging member, or both load engag ing members may be actuated simultaneously in opening or closing movement and in opposite directions relative to each other.

With such universality of available clamp arm movement it will be appreciated that a load may be engaged and deposited in various ways. epending upon the preterence of the operator and the relationship of the load to be engaged to the position of the truck and any obstructions in the vicinity, the load may be engaged, for example, by utilizing one of the clamp arms as a guide to be moved into close relation with one side of a load with the other clamp arm spread outwardly of the op posite side thereof and then actuating said other arm independently into clamping engagement with said opposite side of the load; or, the load may be engaged by spreading the clamp arms to straddle the load with the load approximately centered therebetwen and then actuating both clamp arms simultaneously in clamping movement to engage opposite sides of the load. After the load is engaged it is lifted on the lifting mast and transported to a desired location wherein it is deposited. The load may be side shifted, if desired, relative to the center of the truck and deposited in an off-center location. Under some circumstances there may be insufiicient room on one side of the load to spread the clamp arm engaging that side after deposit of the load, under which circumstance the other side of the load may be disengaged from the opposite clamp arm by spreading that clamp arm independently of the first clamp arm, whereupon the truck may be backed oil from the load. If adequate room is available, the load may be disengaged by spreading both clamp arms following deposit of the load, this being the normal procedure and requiring merely that both control valve units er; and 92 be actuated as illustrated in FIG- URE 5 to spread the clamp arms simultaneously. In operating the unit in very close quarters it may, for example, be desirable to push one or another adjacent loads to a different location to make room for a second load to be subseuently deposited. This can be readily accom plished by actuating one or the other clamp arms outwardly or in an opening direction while retaining the other clamp arm stationary so that the load to be relocated may be pushed to its new location by the outer or non-clamping surface of the actuated clamp arm. In other words, in executing the latter operation one of the arms only can be used to push a load into a desired position without requiring movement of the other arm, which under certain close quarter conditions would otherwise be actuated against some other object in the immediate area it both clamping arms were required to move simultaneously. The availability of independent arm actuation in the present control system can also be used to advantage, for example, when relatively light weight loads are clamped at a high elevated position. Under such circumstances, movement of the load to one side prior to clamping engagement could cause the load to fall from its elevated position. In the use of prior art constructions it is necessary for the operator when handling such loads to center the load in relation to the clamp prior to actuating the clamp arms simultaneously to engage the load. Under such condition, it will be apparent that it the load is not centered one clamp arm will contact one side of the load prior to contact of the other side by the other clamp arm, which may result in a pushing of the load by the first clamp arm prior to engagement by both. This undebirable result is avoided in the present invention by proper utilization of independent clamp arm operation.

It follows from the above discussion that a lift truck which embodies the concepts of the present invention may be used to substantially reduce the time in handling materials and do this with greater safety and efilciency than heretofore.

Although I have disclosed only a single exemplary embodiment, it will be apparent that modifications and rearrangement of parts may be made in my invention by those skilled in the art. Therefore, it should be understood that I intend to cover by the appended claims all modifications, changes, and rearrangement of parts which fall within the spirit and scope of my invention.

I claim:

1. In a load gripping device having first and second load gripping members, means supporting the members for reciprocal movement along a predetermined path, a source of pressure fluid, first and second double-acting 'fiuid motor means connected respectively to the first and second members for actuating the members along the predetermined path and to said source of pressure fluid, control means comprising a first fluid circuit for controlling the movement of the members in unison along the predetermined path, said first fluid circuit including a first control valve connected to the source of pressure fiuid, said first control valve having first and second ports and operable to communicate selectively either said first port, said second port or neither port with the source of pressure fluid, first conduit means for connecting said first port with one end of the first motor means, second conduit means for connecting said second port with one end of port or neither port with the source of pressure fluid,

fourth conduit means for connecting said third port with said third conduit means, fifth conduitimeans for connecting said fourth port with said first conduit means, a first check valve disposed in said fourth conduit'means andoperatin to block fluid flow towards said third port except when said fifth conduit means is in communication with the source of pressure fluid, and a second check valve disposed in said fifth conduit means and operating to block fluid flow toward said fourth port except when said fourth conduit means is in communication with the source of pressure fluid, and a third fluid circuit for con- 1 trolling the movement of the other of the load gripping members along the predetermined path, said third fluid circuit including a third control valve connected to the source of pressure fluid, said third control valve having fifth and sixth ports and operable to communicate selectively either said fifth port, said sixth port or neither port with the source of pressure fluid, sixth conduit means for connecting said fifth port with said third conduittmeans,

seventh conduit means for connecting said sixth port with said second conduit means, a third check valve disposed in said'sixth conduit means and operating to block fluid flow toward said fifth port except when said seventh conduit means is in communication with the source of pressure fluid, and a fourth check valve disposed in said seventh conduit means and operating to block fluid flow toward said sixth port except when said sixth conduit means is in communication with the source of pressure fluid.

2. In a load gripping device having a pair of load-engaging members, first and second fluid motor means for moving said members along a predetermined path, a source of pressure fluid, and fluid circuit means operatively connected to said fluid source and to said motor means for automatically effecting simultaneous movement of said members along said path in the same direction and alternatively in opposed directions, the improvement comprising means for effecting movement of either of said members along said path while maintaining the other member stationary, said movement-eifecting means comprising a pair of fluid circuits connected to each other and to said first and second motor means, a plurality of control valves controlling fluid flow in said circuit means and circuits, and a plurality of check'valve means connected fluidly intermediate said circuit means for automatically preventing flow between the circuit means upon operation of the circuit means or of either of the circuits, each of the second and third valve means comprising a pair of check valve units fluidly connected to each other for allowing flow to the associated motor means in either direction. a i

3. In a load gripping device having first and second loading-engaging members, first and second fluid motor means for moving said members along a predetermined i2 path, a source of pressure fluid, and fluid circuit means operatively connected to said fluid source and to said motor means effecting simultaneous movement of said members along said path either in the same direction or in opposite directions, the improvement comprising first and second, fluid circuits for effecting movement of either of said members along said path while maintaining the other member stationary,-said circuits being connected respectively to said first and second motor means, a plurality of control valves controlling fluid flow in said circuit means and circuits, and a pair of check valves in each circuit for automatically preventing flow between each circuit and portions of the circuit means, one of said control valves being operable to shift the load-engaging members in unison in the same lateral direction and others of the control valve being operable to shift the load-engaging members independently of each other simultaneously in opposite directions.

4. A device as defined in claim 3, wherein said check valves are pilot-unseatable by pressure from one direction to allow flow therethrough from another direction, and the check valves of eachpair are fluidly intercon nected to open one for'return flow ther'ethrough upon flow through the other. A

V S. In a device of the class described, first and second load-engaging members, means supporting said members for movement along a predetermined path, a source of pressure fluid, first and second fluid motor means operatively connected to said source and also connected respectively to said first and second members for effecting movement thereof along said path, first valve means connected to said first and second motor means for operation thereof to move said members in unison in the same direction along said path, second valve means connected to the first motor means for operation thereof independently of the second motor means to move said first member in either direction along said path while maintaining the second member stationary, and third valve means connected to the second motor means for operation thereof independently of the first motor means to move the second member ineither direction along said path while maintaining the first member stationary, said first valve means being operable independently of the second and third valve means, each of the second and third valve means comprising a pair of check valve units fluidly connected to each other for allowing flow to the associated motor means in either direction. 1

References Cited by the Examiner UNITED sTATEs PATENTS 2,782,065i 2/57 Lord 214-731 2,788,148 4/57 Parcell 214-653 2,795,346 6/57 Farmer 214-653 2,918,186 12/59 Cirillo 214 731 2,920,775, 1/60 Schenkelberger 214653 2,984,9 5 5/61 MacMillin 214652 X f FOREIGN PATENTS 717,358 5/52 Great Britain. 879,790 8/60 GreatBritain.

V HUGO O; SCHULZ, Primary Examiner.

MORRIS TEMIN, Examiner,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,184,088 May 18, 1965 Kenneth H. Berge It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 40, for "if" read of line 48, after "valves" insert are column 7, line 54, for "contol" read control column 9, line 4, for "tof" read of line 70, for "therebetwen" read therebetween column 10, line 17, for "subseuently" read subsequently column 11, line 57, beginning with "each of the" strike out all to and including "direction" in line 60, same column 11, and insert instead one of said control valves being operable to shift said loadengaging members in unison in the same lateral direction and others of the control valves being operable to shift the loadengaging members laterally independently of each other and simultaneously in opposite directions Signed and sealed this 23rd day of November 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER \ttesting Officer Commissioner of Patents 

2. IN A LOAD GRIPPING DEVICE HAVING A PAIR OF LOAD-ENGAGING MEMBERS, FIRST AND SECOND FLUID MOTOR MEANS FOR MOVING SAID MEMBERS, ALONG A PREDETERMINED PATH, A SOURCE OF PRESSURE FLUID, AND FLUID CIRCUIT MEANS OPERATIVELY CONNECTED TO SAID FLUID SOURCE AND TO SAID MOTOR MEANS FOR AUTOMATICALLY EFFECTING SIMULTANEOUS MOVEMENT OF SAID MEMBERS ALONG SAID PATH IN THE SAME DIRECTION AND ALTERNATIVELY IN OPPOSED DIRECTIONS, THE IMPROVEMENT COMPRISING MEANS FOR EFFECTING MOVEMENT OF EITHER OF SAID MEMBERS ALONG SAID PATH WHILE MAINTAINING THE OTHER MEMBER STATIONARY, SAID MOVEMENT-EFFECTING MEANS COMPRISING A PAIR OF FLUID CIRCUITS CONNECTED TO EACH OTHER AND TO SAID FIRST AND SECOND MOTOR MEANS, A PLURALITY OF CONTROL VALVES CONTROLLING FLUID FLOW IN SAID CIRCUIT MEANS AND CIRCUITS, AND A PLURALITY OF CHECK VALVE MEANS CONNECTED FLUIDLY INTERMEDIATE SAID CIRCUIT MEANS UPON MATICALLY PREVENTING FLOW BETWEEN THE CIRCUIT MEANS UPON OPERATION OF THE CIRCUIT MEANS OR OF EITHER OF THE CIRCUITS, EACH OF THE SECOND AND THIRD VALVE MEANS COMPRISING A PAIR OF CHECK VALVE UNITS FLUIDLY CONNECTED TO EACH OTHER FOR ALLOWING FLOW TO THE ASSOCIATED MOTOR MEANS IN EITHER DIRECTION. 